In this guide, we will explore the key differences between the original Polygon PoS and Polygon zkEVM, delving into their respective architectures, consensus mechanisms, data availability options, and more. Our goal is to provide a comprehensive understanding of how Polygon zkEVM extends and enhances the broader Polygon ecosystem while addressing the challenges associated with scaling the Ethereum blockchain.
Polygon PoS primarily uses a Plasma framework and a Proof-of-Stake (PoS) consensus mechanism to create a sidechain that runs parallel to the Ethereum mainnet. Polygon zkEVM, on the other hand, uses a ZK-Rollup architecture that leverages zero-knowledge proofs to provide a Layer 2 solution on top of Ethereum.
Polygon PoS relies on a set of validators that participate in the PoS consensus mechanism to validate and confirm transactions on the sidechain. Polygon zkEVM uses a Consensus Contract that supports permissionless participation of multiple coordinators (Sequencers and Aggregators) to produce and validate batches in L2.
In Polygon PoS, data is stored on the sidechain, which provides a separate blockchain for transaction processing. Polygon zkEVM offers two options for data availability under a Hybrid schema: Validium (data is stored off-chain) and Volition (data and validity proofs are on-chain for some transactions and only proofs for others).
Polygon PoS is a sidechain that offers EVM (Ethereum Virtual Machine) compatibility. This means that developers can deploy and run Ethereum smart contracts on the Polygon PoS sidechain. However, EVM compatibility implies that while the sidechain supports Ethereum smart contracts, there may be some differences in the execution environment. As a result, in rare situations when dealing with complex dapps and low-level code developers may need to make certain adaptations or use sidechain-specific features when working with Polygon PoS.
In contrast, Polygon zkEVM is a ZK-Rollup that focuses on achieving EVM equivalence. EVM equivalence implies a higher level of compatibility with Ethereum, allowing existing Ethereum smart contracts to be deployed and run on Polygon zkEVM without any modifications. Developers do not need to change languages or tooling, and they can experience a seamless transition when deploying their smart contracts on the EVM-equivalent rollup. EVM equivalence effectively recreates the entire Ethereum execution environment.
The key distinction is that EVM equivalence, as offered by Polygon zkEVM, provides "less friction" compared to EVM compatibility, as offered by Polygon PoS. Polygon zkEVM is designed to offer transparent deployment and complete Ethereum compatibility, allowing developers to maintain the same development workflow as on Ethereum, without the need for any kind of modification or re-implementation of code. In summary, Polygon zkEVM is focused on being a near-perfect replica of Ethereum's execution environment, while Polygon PoS is focused on offering compatibility with Ethereum smart contracts within the context of a sidechain.
Polygon PoS relies on its PoS validators to secure the sidechain, which operates independently from Ethereum. Polygon zkEVM inherits the security of the Ethereum mainnet by publishing validity proofs on-chain, ensuring that off-chain computations are correct and secure.
Polygon PoS sidechains offer fast transaction finality with relatively low transaction fees. Polygon zkEVM uses zero-knowledge proofs to offer quick finality to off-chain transactions while reducing latency and fees.
While both Polygon PoS and Polygon zkEVM provide Layer 2 scaling solutions for Ethereum, they differ in their architecture, consensus mechanisms, data availability options, and implementation details. Polygon zkEVM, in particular, leverages ZK-Rollup technology to achieve improved scalability, security, and EVM-equivalence while ensuring quick transaction finality.